1. Field of the Invention
This invention relates to systems for providing electronic documents, and more particularly to document delivery systems wherein servers transcode documents delivered to client machines.
2. Description of Related Art
The World Wide Web, known simply as the xe2x80x9cWebxe2x80x9d, is a network of Internet servers that provide specially formatted electronic documents to various xe2x80x9cclientxe2x80x9d machines. Web servers currently support documents formatted in a text-based markup language called hypertext markup language (HTML).
In order to provide Web access to client machines with limited capabilities (e.g., palmtop or handheld computers), a xe2x80x9ctranscoder proxyxe2x80x9d is typically positioned between the client machine and an Internet server. The transcoder proxy may, for example, provide selected portions of a requested Web document to the client machine based upon the capabilities of the client machine. In doing so, the transcoder proxy may translate one or more selected portions of the Web document from one digital format to another.
FIG. 1 is a block diagram of a representative system 10 currently used to provide an electronic document 12 (e.g., a Web page) to a client machine 14 with limited capabilities. Client machine 14 may be, for example, a palmtop or handheld computer with limited memory, processing capability, and/or display capability. System 10 includes an internet server 16, and a transcoder proxy 18 interposed between client machine 14 and internet server 16. Transcoder proxy 18 forwards a request for document 12 from client machine 14 to internet server 16. Such a request typically includes a uniform resource locator (URL) of document 12 specifying the internet protocol (IP) address of document 12 and the name of the file containing document 12.
Internet server 16 fetches document 12 and provides document 12 to transcoder proxy 18. Based upon the capabilities of client machine 14, transcoder proxy 18 may translate or xe2x80x9ctranscodexe2x80x9d one or more selected portions of document 12 from one digital format to another. For example, transcoder proxy 18 may transcode a portion of document 12 from HTML to a script written in a scripting language understood by a Web browser application program running within client machine 14. The Web browser program may use information conveyed by the script to present the one or more selected portions of document 12 upon a display device of client machine 14.
Alternately, client machine 14 may include a text-to-speech converter, and the information conveyed by the script may be used to output the one or more selected portions of document 12 as speech through a speaker of client machine 14. The term xe2x80x9cassistive technologyxe2x80x9d is used herein to describe technology that helps physically challenged individuals access to a computer system (e.g., client machine 14). Well known types of assistive technologies include xe2x80x9cscreen readersxe2x80x9d which convert display information to speech, xe2x80x9cscreen magnifiersxe2x80x9d which enlarge features of portions of display screen contents, and voice recognition software which converts speech to a digital representation of text or commands.
Computer language code or xe2x80x9cscriptxe2x80x9d which modifies visual presentations of electronic documents in response to user input is increasingly being included within electronic documents. Such interactive aspects of electronic documents are used to provide, for example, Web site navigation information in response to user input. JAVASCRIPT ((trademark) Netscape Comm. Corp., Mountain View, Calif.) is a well known cross-platform, object-based scripting language for client and server applications. JAVASCRIPT is commonly used to add interactive aspects to electronic documents such as Webpages.
The Document Object Model (DOM) is an application programming interface (API) for xe2x80x9cdocumentsxe2x80x9d. The World Wide Web Consortium (W3C) has authored a DOM specification available on the Web at URL http://www.w3.org/. The DOM defines the logical structure of documents and the way a document is accessed and manipulated. In the DOM specification, the term xe2x80x9cdocumentxe2x80x9d is used in the broad sense. Increasingly, XML is being used as a way of representing many different kinds of information that may be stored in diverse systems. Much of this information would traditionally be seen as data rather than as documents.
In the DOM, documents have a logical structure which is very much like a tree. To be more precise, the logical structure is like a xe2x80x9cforestxe2x80x9d or xe2x80x9cgrovexe2x80x9d, which can contain more than one tree. However, the DOM specification does not require that documents be implemented as a tree or a grove, nor does it specify how the relationships among objects be implemented. The DOM is a logical model that may be implemented in any convenient manner. In the DOM specification, the term xe2x80x9cstructure modelxe2x80x9d is used to describe the tree-like representation of a document. Terms like xe2x80x9ctreexe2x80x9d or xe2x80x9cgrovexe2x80x9d are not used to avoid implying a particular implementation. One important property of DOM structure models is structural isomorphism. If any two DOM implementations are used to create a representation of the same document, they will create the same structure model, with precisely the same objects and relationships.
In current document delivery systems, a problem arises in that many client machines do not support interactive aspects of electronic documents such as Web pages due to resource limitations. As a result, transcoding proxy 18 may be configured to remove any computer language code or script within the one or more selected portions of an electronic document provided to client machine 14. Web site navigation capability may be lost, and with it the ability to access Web site information. Additionally, a client machine may not have sufficient resources to provide an assistive technology solution for a physically challenged user.
It would thus be desirable to have an electronic document delivery system which allows a client machine with limited resources to provide interactive aspects of electronic documents such as Web pages and/or an assistive technology solution for a physically challenged user. The desired document delivery system may use the document object model (DOM) to define a logical structure of an electronic document, and to access and manipulate the electronic document.
Several different embodiments of an electronic document delivery system are described including a client machine coupled to (i.e., in wired or wireless communication with) a transcoder proxy. The client machine may be, for example, a palmtop or handheld computer or a wireless communication device with limited display, memory, and/or processing capability. The transcoder proxy is coupled to receive electronic documents. Each electronic document includes one or more elements, and is expressed in a first digital format (e.g., a text-based markup language such as HTML or XML). The transcoder proxy assigns a unique identifier to each element of the electronic document. The transcoder proxy produces an xe2x80x9coriginalxe2x80x9d script including at least a portion of the electronic document expressed in a second digital format (e.g., a scripting language). The original script includes the elements within the portion of the electronic document, as well as the identifiers assigned to the elements. The transcoder proxy provides the original script to the client machine.
The transcoder proxy may form a model of a logical structure of the electronic document. The model may also define methods for accessing and manipulating the document. The model may be, for example, a document object model (DOM). The transcoder proxy may use the model to produce the original script. The transcoder proxy may save the model, including the elements of the electronic document, and the identifiers assigned to the elements for future use.
The client machine receives the original script from the transcoder proxy, and uses the original script to display or otherwise present the portion of the electronic document. The client machine also generates events in response to user input. The client machine associates an event with an element within the original script. The client machine provides the event and the identifier assigned to the element associated with the event to the transcoder proxy.
The transcoder proxy stores the model, including the elements of the electronic document, and the identifiers assigned to the elements. The elements of the electronic document may be associated with corresponding identifiers within the model. In response to the event and the identifier received from the client machine, the transcoder proxy accesses the model using the identifier. The transcoder proxy may modify the model. Following any modification of the model, the transcoder proxy uses the model to produce a xe2x80x9cmodificationxe2x80x9d script, wherein the modification script differs from the original script. The transcoder proxy provides the modification script to the client machine. The client machine receives the modification script, and uses the modification script to modify the displayed or otherwise presented portion of the electronic document.
One embodiment of the transcoder proxy includes a synchronous document object model (DOM) generator coupled to a transcoder and a user interface generator. The synchronous (DOM) generator is coupled to receive the electronic document, and includes an identifier (ID) generator for assigning a unique identifier to each element of the electronic document. The synchronous DOM generator forms a pre-transcoded DOM representing the logical structure of the electronic document. The pre-transcoded DOM may also define methods for accessing and manipulating the document. Within the pre-transcoded DOM, document elements are associated with corresponding identifiers. The synchronous DOM generator provides a first portion of the electronic document to the transcoder in the first digital format.
The transcoder receives the first portion of the electronic document, and translates the first portion of the electronic document from the first digital format, thereby producing the original script in a second digital format (e.g., a scripting language). As described above, the original script includes the elements within the first portion of the electronic document and the identifiers assigned to the elements. The transcoder provides the original script (e.g., to a client machine coupled to the transcoder).
The user interface generator receives an event and the associated identifier (e.g., from a client machine coupled to the user interface generator). The user interface generator may use the event and the associated identifier to produce DOM access commands, and may provide the DOM access commands to the synchronous DOM generator. In this case, the synchronous DOM generator accesses the pre-transcoded DOM using the DOM access commands. The synchronous DOM generator may modify the pre-transcoded DOM in response to the DOM access commands. Following any modification of the pre-transcoded DOM, the synchronous DOM generator provides a second portion of the electronic document to the transcoder in the first digital format.
The transcoder receives the second portion of the electronic document, and translates the second portion of the electronic document from the first digital format, thereby producing a modification script in the second digital format. The transcoder provides the modification script (e.g., to the client machine).
One embodiment of the client machine includes a user agent coupled to an output device. The output device may be, for example, a display device for visual presentation. Alternately, the output device may be a text-to-speech converter for audible presentation. The user agent is also adapted for coupling to the transcoder proxy. The user agent receives the original script from the transcoder proxy, and forms a transcoded DOM in response to the original script. The transcoded DOM is a representation of the first portion of the electronic document. The user agent uses the transcoded DOM to produce output commands, and provides the output commands to the output device.
In response to user input, the user agent generates an event. The user agent associates the event with an element within the original script. The user agent provides the event and the identifier assigned to the element associated with the event to the transcoder proxy. The user agent receives the modification script from the transcoder proxy, and modifies the transcoded DOM in response to the modification script. As a result, the portion of the electronic document displayed or otherwise presented by the output device is modified.
A method for transcoding an electronic document, which may be embodied within the transcoder proxy, includes receiving the electronic document in a first digital format (e.g., a text-based markup language such as HTML or XML). A unique identifier is assigned to each element of the electronic document. A model of a logical structure of the electronic document is formed. The model may also define methods for accessing and manipulating the document. The model may be, for example, a document object model (DOM). The model includes the identifier assigned to each element. The model is used to produce a script, wherein the script includes at least a portion of the document expressed in a second digital format (e.g., a scripting language). The script includes at least one element, and the identifier assigned to the element. The script is provided (e.g., to a client machine).
A first method for presenting an electronic document, which may be embodied within the transcoder proxy, includes the above transcoding method, wherein the script produced using the transcoding method is an original script. The presentation method further includes receiving an event and an identifier associated with the event (e.g., from a client machine). The model is accessed using the identifier associated with the event, and may be modified. Following any modification, the model is used to produce a modification script, wherein the modification script differs from the original script. The modification script is provided (e.g., to the client machine).
A second method for presenting a electronic document, which may be embodied within the client machine, includes receiving an original script (e.g., from a transcoder proxy), wherein the original script includes at least a portion of the electronic document expressed in a digital format (e.g., a scripting language). The original script is used to present the portion of the electronic document. An event is generated in response to user input. The event is associated with an element within the original script. The event and the identifier assigned to the element are provided (e.g., to the transcoder proxy) in response to the event. A modification script is received (e.g., from the transcoder proxy), wherein the modification script differs from the original script. The modification script is used to modify the presented portion of the electronic document.